In general, vehicle drivelines transmit torque from a vehicle's engine to its wheels. Automotive drivelines, such as all-wheel drive (AWD) drivelines, commonly employ final drive units (FDUs) for transmitting torque to left and right sideshafts that are located downstream an engine and downstream a transmission—oftentimes, FDUs receive driven torque from a propshaft. Final drive units can be mounted at the rear of an automotive driveline or at the front, depending on the architecture of the particular driveline and the location of its engine and transmission. And FDUs can include differential gearsets that allow wheels on one sideshaft to spin faster or slower than wheels on the other sideshaft, and that apportion driven torque between the sideshafts.
Furthermore, some automotive drivelines are equipped with disconnect capabilities in which disconnected components are no longer driven to transmit torque between them. The capabilities preclude driven torque in regions of the automotive drivelines not needing torque at a particular time. For instance, on-demand AWD drivelines do not always transmit torque among all of its shafts at all times. Disconnect capabilities have been shown to increase fuel mileage, reduce emissions, and provide additional performance improvements. In FDUs, disconnect capabilities can be carried out via one or more wet clutches furnished between a final drive gearset and a sideshaft. Wet clutches typically include multiple clutch plates that are brought together to connect components, and brought apart to disconnect components. Lubricant is supplied to the clutch plates amid these actions.
But it has been found that clutch plates and components that should not be rotating when disconnected, still have a tendency to rotate even when the plates are brought apart. Lubricant between the separated clutch plates, it has been learned, produces adhesion and sticking between neighboring plates. When an automobile is traveling on a road, its wheels and sideshafts spin. The spinning sideshaft at a wet clutch rotates some of its plates—an event known as backdriving. And the adhesion between clutch plates can cause unwanted rotation of all the plates and components in the FDU. The unwanted rotations contribute to drag loss experienced in the driveline and ultimately diminish the efficiency of the driveline.